The shuttered St. John’s Episcopal Church, a 143-year old Jersey City structure once known as “the millionaire’s church” because of its well-heeled congregation, has been named a local landmark by the City Council.

The council tonight unanimously approved a measure designating the church a historic landmark, which will require its owners, the Episcopal Diocese of Newark, to seek approval from the local Historic Preservation Commission before altering or demolishing the building.

The diocese, which could not be reached to comment, objects to the designation, saying the Summit Avenue church is too dilapidated to be saved. But local preservationists, who have been lobbying for the landmark designation for years, said tonight that the church must be saved.

There are eight other local landmarks, including the Apple Tree House, the 6th Street Embankment and Ellis Island.

St. John's played a pivotal role for African Americans in Jersey City during the civil-rights movement. The Rev. Robert W. Castle Jr., rector at St. John’s from 1960 to 1968, opened his home to the Black Panthers and picketed businesses for not hiring blacks.

Wegman Parkway resident Virginia Miller said she met with other civil-rights activists at the church almost daily during those years as Castle and others discussed where to picket in Jersey City.

If the church is torn down, Miller said, “a piece of history would be destroyed and we would have another vacant lot in our community.”

The Gothic structure closed its doors in 1994. In 2007, the planning board unanimously recommended naming the church a local landmark. A subsequent vote by the council in 2008 affirmed that recommendation, but the council never adopted the measure.

Councilwoman at large Viola Richardson asked last month that it return to the council’s agenda, and tonight local historian John Gomez, a columnist for The Jersey Journal, called Richardson “my preservation hero.”

Diocese spokeswoman Nina Nicholson has previously said the diocese cannot afford to make repairs to the building.

“It’s well established the building is unsafe and has been unsafe,” she said. “It needs to be demolished.

John J. Hallanan, president of the Jersey City Landmarks Conservancy, tonight accused the diocese of neglecting the building intentionally to pave the way for demolition. The church is structurally sound, he said, and can be converted into housing or even a public pool while keeping its historic nature intact.